Smoking isn’t just bad for your body — it could be bad for your mind, too. A study published in the Archives of General Psychiatry shows smoking is linked to a faster, more dramatic age-related mental decline in men.

In the study, scientists from the University College in London analyzed data from nearly 6,000 men and more than 2,000 women who were given mental assessments that included five tests of memory, vocabulary, and reasoning (verbal and math) skills. The tests were first done when the volunteers were an average age of 56, and then twice more at five-year intervals.

To determine volunteers’ smoking habits over a 25-year period, researchers looked at their then current smoking status and past history, including whether they had quit or relapsed.

Results showed there was a faster mental decline in middle-aged men who currently smoked than men who never did. In particular, smoking seemed to speed up the cognitive aging process, making men function mentally as if they were 10 years older, said Severine Sabia, the study’s lead author.

“For example, a 50-year-old male smoker shows a similar cognitive decline as a 60-year-old male never-smoker,” she told ABC News.

The good news is that the damage may not be permanent, but reversing it may take some time. Men who stopped smoking more than 10 years before the tests performed as well as those who had never smoked — but men who kicked the smoking habit less than 10 years before the cognitive tests began didn’t do much better than the men who’d kept smoking.

The link between smoking and mental decline isn’t terribly surprising — lighting up is a risk factor for dementia, and it also increases the odds of developing heart and lung disease, two health problems also associated with memory difficulties.